R正则表达式存储变量? [英] R regex store variables?

问题描述

是否可以在 R 的正则表达式中使用存储变量?

Is it possible to use stored variables in R's regex?

例如，我想删除以下字符串中十进制数字周围的引号 s = "\"Bob\",\"1\",\"Mary\",\"2\"" - 在大多数语言中，您可以执行诸如 sub("\"(\d)\"","$1",s) 之类的操作，但我似乎找不到 R 中的功能.任何帮助都会不胜感激.

For example I want to remove quotes around decimal numbers in the following string s = "\"Bob\",\"1\",\"Mary\",\"2\"" - in most languages you could do something like sub("\"(\d)\"","$1",s) but I cannot seem to find the capability in R. Any help would be greatly appreciated.

还有一个附带问题，R 是否支持 \d?(当我尝试时它会抛出错误)谢谢

Also as a side question does R have the \d support? (it throws an error when i try it) Thanks

推荐答案

我相信这通常被称为回引用.在 R 中，您可以使用 \\1 \\2 等.

I believe this is usually called back referencing. In R, you can use \\1 \\2, etc.

re.examples <- c(
    'What_are_we_doing?',
    'Woe, that a young fowl should fly the coop',
    '2011/12/24',
    'Subject: More information, then less important stuff.' 
)

sub("([0-9]+)/([0-9]+)/([0-9]+)","Year is \\1 Month is \\2 Day is \\3",re.examples[3])
sub("^([A-Za-z ]+): ([A-Za-z ]+), ([A-Za-z ]+).$","\\2",re.examples[4])

<小时>

我不确定 R 中的 \d 支持.无论如何我通常只使用 [0-9]，因为我知道它有效并且我发现它更易于阅读.

---

I'm not sure about \d support in R. I generally just use [0-9] anyway, since I know it works and I find it easier to read.

@Andrie 和@Richie Cotton 都在评论中提供了两个建议，为了完整起见，我将在此处包含这些建议.[:digits:] 有效，但在我看来，[0-9] 的可读性很少.\\d 也可以.

@Andrie and @Richie Cotton both offered two suggestions in comments, which I will include here for completeness. [:digits:] works, but to my mind offers little in readability over [0-9]. \\d works as well.

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